Two New Polymethoxylated Flavones, a Class of Compounds with Potential Anticancer Activity, Isolated from Cold Pressed Dancy Tangerine Peel Oil Solids

Abstract

Ten polymethoxylated flavonoids were isolated and characterized from cold pressed tangerine oil solids; they are 5,6,7,3‘,4‘-pentamethoxyflavone (sinensetin) (I); 7-hydroxy-3,5,6,3‘,4‘-pentamethoxyflavone (II); 5-hydroxy-6,7,8,3‘,4‘-pentamethoxyflavone (III); 5,6,7,8,3‘,4‘-hexamethoxyflavone (nobiletin) (IV); 5,6,7,8,4‘-pentamethoxyflavone (tangeretin) (V); 5,7,8,4‘-tetramethoxyflavone (tetra-O-methylisoscutellarein) (VI); 7-hydroxy-3,5,6,8,3‘,4‘-hexamethoxyflavone (VII); 5,6,7,4‘-tetramethoxyflavone (tetra-O-methylisoscutellarein) (VIII); 3,5,6,7,8,3‘,4‘-heptamethoxyflavone (IX); and 5,7,8,3‘,4‘-pentamethoxyflavone (X). Structures of the compounds were elucidated on the basis of spectroscopic methods and chemical data. Compounds II and VII are novel natural products; compounds IV, V, and VIII have been reported with significant activity against various strains of carcinoma cells; and compounds I and IV decrease erythrocyte aggregation and sedimentation in vitro. A biological activity screen of other compounds is in progress. Keywords: Polymethoxylated flavones; antitumor activity; Citrus; tangerine oils; Dancy tangerine